End fitting for hose

ABSTRACT

A method of securing an end fitting ( 10 ) to an end of a hose ( 12 ) having an outer braid ( 12   a ) and a plastic liner ( 12   b ) is disclosed, the method including the step of: i) providing a hollow end fitting ( 10 ) for a hose ( 12 ), the end fitting ( 10 ) having a spigot ( 10   a ) and a sealing face; ii) inserting the spigot ( 10   a ) of the end fitting ( 10 ) between the braid and the liner( 12   b ) and bring the liner end through said hollow end fitting ( 10 ) and flaring out the liner end to form a plastic sealing face; iii) processing the assembly so formed in such a manner as to cause the flared liner end to form a shape which includes a bead ( 26 ) on the liner surface and which has its inside edge ( 28 ) squared off. The bead ( 26 ) is preferably concentric and allows the rubber seal previously used to be dispensed with. The end fitting ( 10 ) preferably comprises a PTFE lined end fitting, in which the PTFE hose liner ( 12   b ) is passed through the bore of the end fitting ( 10 ), and is then flared out. A plastic lined hose ( 12 ) is also disclosed having secured to an end thereof a hollow end fitting ( 10 ) having a spigot ( 10   a ) and a sealing face ( 10   b ), wherein the spigot ( 10   a ) is located between the braid ( 12   a ) and the liner( 12   b ), and the liner end passes through the end fitting ( 10 ) and is flared out to form a plastic sealing face overlying the sealing face ( 10   b ) of the end fitting ( 10 ) to form a shape which includes a bead ( 26 ) on the liner surface and which has its inside edge ( 28 ) squared off.

The present invention relates to a method of securing an end fitting toa flexible hose or pipe, in particular a plastic hose, and to anassembly comprising a plastic lined hose having an end fitting securedthereto.

The type of end fitting to which this invention relates primarily,thought not exclusively, is that know as “Triclover”, “Triclamp” or“clamp type” as defined by British Standard BS 4825 Part 3. This type ofend fitting is widely used in biochemical process plants andlaboratories where the ultimate in hygienic operation is required.

Conventionally, an end fitting of this type would be secured to the endof a pipe or hose to provide a means of connection to other pipes andhoses. One way in which this is currently done is to insert an endfitting within the hose end and align it with an identical end fitting,clamping the two components together with a rubber seal located betweenthe sealing faces of the two end fittings. This rubber sealconventionally includes annular “beads” on each face which seat withincorresponding machined grooves in the steel end fittings, these beadsproviding an aid to concentric location during assembly. This system hasthe disadvantage that the fitting creates an entrapment zone for fluidpassing through the fitting, such as renders hygienic operationimpossible. See FIG. 1 of the accompanying drawings.

It is also known to attach such an end fitting to say a fluorocarbon orPTFE plastic lined hose in such a way that the plastic liner is passedthrough the bore of the fitting, then flared out to form a sealing face,thus ensuring continuity of hygienic fluid flow through the fitting, andto protect the fitting from any corrosive effect the fluid may have onthe material from which the fitting itself is made. See FIG. 2 of theaccompanying drawings.

However, there is a disadvantage in this second type of procedure inthat, because it eliminates the rubber seal and hence the “beads”,concentric connection of the two end fittings is relatively difficultand also requires a much greater clamping force for form a seal with thefluorocarbon plastic sealing face than would otherwise be required witha softer, more resilient, rubber seal. The clamping system usedconventionally is not designed to provide such a high clamping force.Also, an entrapment zone is created at the point where the PTFE linergoes around the corner of the end fitting into the flared sealing face.

Our European patent publication number EP 0707170 disclosed a systemwhich is easily aligned concentrically and which can be sealedeffectively using conventional clamping techniques. Furthermore, thissystem eliminates entrapment zones. See FIG. 3 of the accompanyingdrawings.

The latter system suffered from the disadvantage, however, that a rubberseal was still required to form a seal, so that any fluid passingthrough which was not compatible with rubber would create problems.

It is not practical to substitute a rubber seal with a PTFE seal (whichhas much better chemical resistance) since this design of seal is veryexpensive, not readily available, and notoriously unreliable in service.

The aim of the present invention, therefore, is to provide a Tricloverend fitting design attached to a PTFE lined hose which overcomes theproblems referred to above.

According to a first aspect of the present invention there is provided amethod of securing an end fitting to an end of a hose having an outerbraid and a plastic liner, the method including the steps of:

-   -   i) providing a hollow end fitting for a hose, the end fitting        having a spigot and a sealing face;    -   ii) inserting the spigot of the end fitting between the braid        and the liner and bring the liner end through said hollow end        fitting and flaring out the liner end to form a plastic sealing        face;    -   iii) processing the assembly so formed in such a manner as to        cause the flared liner end to form a shape which includes a bead        on the liner surface and which has its inside edge squared off.

The bead is preferably concentric and allows the rubber seal previouslyused to be dispensed with.

The face of the end fitting may or may not have a bead machined in it asdescribed more fully hereinafter.

This end fitting preferably comprises a PTFE lined end fitting, in whichthe PTFE hose liner is passed through the bore of the end fitting, andis then flared out.

This flared out portion may then be hot formed, e.g. by pressing with aheated tool, in order to form a shape which includes a “bead” of PTFE,and has the inside edge squared off. This bead can be either formed withor without a corresponding bead machined in to the face of the steel.

The differences of the fitting of the invention over that disclosed inour above mentioned European patent are:

-   -   1. the steel flange behind the PTFE is thicker by the thickness        of the rubber seal, so as to produce an overall thickness of        fitting in which the rubber seal is no longer required; and    -   2. the hot forming produces a bead, instead of a pocket for the        bead on the rubber seal to sit in.

Thus, the end fitting (typically a steel end fitting) applied inaccordance with the invention may be located concentrically with astandard conventional end fitting having a similar groove in its sealingface without using a conventional resilient rubber seal having annularbeads on each sealing face which are received within the annular groovesin the plastic liner and the sealing face of the conventional endfitting respectively. The two end fittings may then be clamped togetherto form a sealed connection.

The processing step also preferably results in the liner assuming asquare internal corner where it goes into the flared sealing face, thusavoiding any entrapment zone.

Conveniently, the processing step (iii) recited above is a hot coiningprocess which causes the plastic liner to assume the shape of the rubberseal.

The clamping system used would typically be a clamp ring which pressesthe two end fittings together.

According to a second aspect of the present invention, there is provideda plastic lined hose having secured to an end thereof a hollow endfitting having a spigot and a sealing face, wherein the spigot islocated between the braid and the liner, and the liner end passesthrough the end fitting and is flared out to form a plastic sealing faceoverlying the sealing face of the end fitting to form a shape whichincludes a bead on the liner surface and which has its inside edgesquared off.

The hot-formed face of the of the seal includes a bead to ensureconcentric location of the jointed component, and provides a squared-offinside edge to eliminate an entrapment zone. Also, because the sealingsurface of PTFE has been hot-formed flat and smooth, it has beendiscovered that the clamping force needed to make an effective sealagainst internal pressure is much lower, and is within acceptable limitsrequired by users who are used to the clamping forces necessary forrubber seals.

Another advantage of the invention over any design which inorporates aseal, whether rubber or PTFE, is that there is only one sealing surface,not two, thereby halving the opportunities for leakage.

The invention will be described further, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 illustrates a conventional method of attaching a hose with an endfitting to a pipe with a conventional end fitting;

FIG. 2 illustrates a different conventional method of attaching a hosewith a plastic lined and flared end fitting to a pipe with aconventional end fitting;

FIG. 3 illustrates an end fitting and method of securing the same inaccordance with European Patent publication no. 0707170; and

FIGS. 4 a and 4 b are similar views to FIG. 3 showing two embodiments ofthe method and joint of the present invention.

Referring to the drawings, and in particular FIG. 1, an end fitting 10is conventionally applied to the end of a hose 12 (which may comprise anouter layer 12 a, normally a comprising a braid, and an inner layer 12b), by inserting the spigot end 10 a inside the liner 12 b and clampingthe end fitting 10 to another end fitting 14 using a clamp ring 16 topress the two seal faces 10 b,14 b together against a rubber seal 15.The seal 15 has two annular beads 15 b extending outwardly from the sealfaces, and these two beads 15 b are received inside grooves 10 c, 14 cin the respective end fittings, thus acting as a guide to concentricalignment. This arrangement creates an entrapment zone 17 between theliner 12 b and the end of the spigot 10 a, in which debris may collect.

Turning now to FIG. 2, an arrangement known as a “flared plastic linedend” is illustrated, in which the liner 12 b is pulled through thehollow end fitting 10 and flared out to form a seal between the twofaces 10 b,14 b of the two end fittings. This seal can then be clamped,again using a clamp ring 16. This avoids the entrapment zone problemwith the construction shown above, but is difficult to align correctlyand to clamp using the conventional clamp ring 16 owing to the highersealing force required. Also, another entrapment zone 17 is createdbetween the liner 12 b and the sealing face 14 b of the mating endfitting 14.

The construction illustrated in FIG. 3 overcomes the above difficultiesby providing a modified end fitting 20 in which the whole of the sealingface of the end fitting is machined back, and the groove 20 c re-formedor enlarged. The flared end of the plastic liner 13 b is then “hotcoined” to cause it to mould itself into and assume the shape of theunderlying recess face of the end fitting 20, including the groove 20 c.

Thus, the face of the end fitting 20 is still lined with plasticmaterial, for example, PTFE, as with the prior embodiment illustrated inFIG. 2, but also includes in that lined face a groove 13 c formed in theliner 13 b to receive the annular bead of a rubber seal 22. Thus, theend fitting 20 can be clamped to a conventional end fitting 14 using aconventional clamp ring 16 and conventional rubber seal 22.

Turning now to FIG. 4 a and using like numbers for like parts, the hoseand seal arrangement in accordance with the invention is illustrated, inwhich the end face 10 b of the end fitting 10 is machined with aconcentric bead 24 machined therein. The liner 12 b is pulled throughthe hollow end fitting 10 as before and flared out. The flared outportion is then hot formed by pressing with a heated tool in order toform a shape which includes a bead 26 of PTFE, and has the inside edge28 squared off. The outer layer 12 a, being a braid reinforcement, ispassed over the top of the spigot 10 a and locked thereto by crimping anexternal ferrule 30 radially inwards to squeeze and hold the braidpermanently to the spigot.

The end fitting 10 is modified in that the steel flange behind the PTFE15 is thicker by the thickness of the rubber seal which would otherwisebe provided so as to produce an overall thickness of fitting in whichthe rubber seal is no longer required. The bead 26 takes the place ofthe bead of the rubber seal 15.

Turning now to FIG. 4 b, the construction of this embodiment isidentical, except that the machined bead 24 is omitted, the surface 10 bbeing flat. This therefore means that the PTFE bead 26 is solid ratherthan hollow as in the construction of FIG. 4 a.

The end fitting of the invention provides a simple, inexpensive andeffective way of producing a seal with a PTFE lined pipe fitting whereinentrapment zones are eliminated and the clamping forces required are notexcessive.

1. A method of securing an end fitting to an end of a hose having anouter braid and a plastic liner, the method including the steps of: i)providing a hollow end fitting for a hose, the end fitting having aspigot and a sealing face; ii) inserting the spigot of the end fittingbetween the braid and the liner and bring the liner end through saidhollow end fitting and flaring out the liner end to form a plasticsealing face; iii) processing the assembly so formed in such a manner asto cause the flared liner end to form a shape which includes a bead onthe liner surface and which has its inside edge squared off.
 2. A methodas claimed in claim 1 wherein the bead is concentric and allows therubber seal previously used to be dispensed with.
 3. A method as claimedin claim 2 wherein the end fitting comprises a PTFE lined end fitting,in which the PTFE hose liner is passed through the bore of the endfitting, and is then flared out.
 4. A method as claimed in claim 3wherein the flared out portion is hot formed, e.g., by pressing with aheated tool to form a shape which includes a “bead” of PTFE, and has theinside edge squared off.
 5. A method as claimed in claim 4 wherein thebead is formed with a corresponding bead machined in to the face of thesteel.
 6. A method as claimed in claim 4 wherein the bead is formedwithout a corresponding bead machined in to the face of the steel.
 7. Amethod as claimed in claim 1 wherein the processing step (iii) alsoresults in the liner assuming a square internal corner where it goesinto the flared sealing face, thus avoiding any entrapment zone.
 8. Amethod as claimed in claim 1 wherein step (iii) is a hot coining processwhich causes the plastic liner to assume the shape of the rubber seal.9. A plastic lined hose having secured to an end thereof a hollow endfitting having a spigot and a sealing face, wherein the spigot islocated between the braid and the liner, and the liner end passesthrough the end fitting and is flared out to form a plastic sealing faceoverlaying the sealing face of the end fitting to form a shape whichincludes a bead on the liner surface and which has its inside edgesquared off.
 10. A hose as claimed in claim 9 wherein the face of theseal includes a bead to ensure concentric location of the jointedcomponent, and provides a squared-off inside edge to eliminate anentrapment zone.